A vulcanization accelerator for rubber is synthesized using a fossil resource such as petroleum or the like as a starting material. In consideration of stable supply of fossil resources, price escalation thereof and the like in future, a vulcanization accelerator not using a fossil resource as a starting material is desired. A technique of using, as a vulcanization accelerator, an amino acid made from a biomass material, is disclosed in PTL 1 and 2 mentioned below, which, however, is problematic in that the amino acid could not sufficiently provide an effect as a vulcanization acceleration efficiency improving agent.
Recently, in association with the movement of global regulation of carbon dioxide emission associated with the increase in attraction to environmental concerns, the demand for low fuel consumption by automobiles is increasing. To satisfy the requirement, it is desired to reduce the rolling resistance of tires. As a method for reducing the rolling resistance of tires, there is mentioned a method of applying a rubber composition having a low-heat-generation property to tires.
As a method of obtaining a rubber composition having a low-heat-generation property, there is mentioned a method of using, for a rubber composition of a synthetic dienic rubber, a polymer that has an increased affinity to carbon black and silica (for example, see PTL 3). For a natural rubber, there is mentioned a method of incorporating a highly-reactive carbon black to a modified natural rubber prepared by modifying a natural rubber (for example, see PTL 4).
According to PTL 3 and 4, the heat-generation property of a rubber composition can be lowered by increasing the affinity of the rubber component to the filler such as carbon black or the like. Accordingly, tires having a low hysteresis loss can be obtained.
However, with further advance of low fuel consumption by automobiles, it is desired to further improve the low-heat-generation property of tires.